KR101216373B1 - Ceria material and method of forming same - Google Patents

Abstract

A particulate material comprising cerium oxide particles having a secondary particle size distribution ranging from 80 nm to 199 nm and having a density of at least 6.6 g / cm ³ .

Description

Ceria material and its formation method {CERIA MATERIAL AND METHOD OF FORMING SAME}

The present invention relates generally to ceria materials and methods and systems for forming ceria materials.

Abrasive materials are used in a variety of industries to remove bulk materials or to affect the surface properties of products, such as shine, texture, and uniformity. For example, metal part manufacturers use abrasives to improve and polish the surface to a uniformly smooth surface. Similarly, optical manufacturers use abrasive materials to create flawless surfaces that prevent unwanted light diffraction and scattering. Additionally, semiconductor manufacturers can polish the substrate material to create low defect surfaces for forming circuit components.

Manufacturers typically want abrasive materials with high stock removal rates for certain applications. However, there is often a trade-off between the removal rate and the quality of the polished surface. Finer particles of abrasive material typically produce a smoother surface, but may have a lower material removal rate. Lower material removal rates lead to slower production and increased costs. On the other hand, larger grain abrasive materials have a higher material removal rate, but may contribute to scratches, pit and other deformations on the polished surface.

Cerium oxide (IV) or ceria is ceramic fine particles used to polish the SiO ₂ -based composition. In general, ceria removes SiO ₂ during polishing by mechanical means. In addition, its chemical activity on SiO ₂ improves the removal rate compared to other materials. In order to use ceria-based particles in electronic applications, such as semiconductor chemical-mechanical polishing (CMP), photomask polishing, or hard disk polishing, these particles may be scratched, pit or otherwise applied to the polished surface. It must be abrasive enough to grind at high speeds without causing deformation, and further free of contaminants. Such defects and contaminants are of increasing importance as device fabrication techniques continue to reduce the minimum feature size.

As such, improved abrasive particulates and abrasive slurries formed therefrom would be desirable.

In certain embodiments, the particulate material comprises cerium oxide particles having a primary particle size in a range from about 70 nm to about 120 nm and a secondary particle size distribution in a range from about 80 nm to about 150 nm.

In another embodiment, the particulate material comprises cerium oxide particles having a primary particle size in a range from about 70 nm to about 120 nm and a density of at least about 6.6 g / cm ³ .

In further embodiments, the particulate material comprises cerium oxide particles having a secondary particle size distribution ranging from about 80 nm to about 199 nm and having a density of at least about 6.6 g / cm ³ .

In further embodiments, the polishing slurry comprises particulate material. The particulate material comprises cerium oxide particles having a secondary particle size distribution ranging from about 80 nm to about 199 nm and having a density of at least about 6.6 g / cm ³ .

In yet another embodiment, a method of forming a ceria material comprises mixing an alkali base with an aqueous solution of cerium nitrate, aging the mixture to form cerium oxide particles, washing the mixture to at least have an ionic conductivity of at least Bringing to about 500 μS / cm, and calcining the cerium oxide particles at a temperature in the range of 650 ° C. to 1000 ° C.

The present invention may be well understood by reference to the accompanying drawings, and many features and advantages of the present invention will become apparent to those skilled in the art.
1, 2, 3, 4, 5, 6, 7, 7, 8, and 9 include images of particles generated using different process parameters.

In certain embodiments, a method of forming cerium oxide fine particles for use in an abrasive slurry comprises mixing an alkali base with an aqueous solution of cerium nitrate; Aging the mixture to form cerium oxide fine particles; Washing the mixture to provide an ionic conductivity of at least about 500 μS / cm; And drying and calcining the cerium oxide particles. In one example, the alkaline base may comprise potassium hydroxide. As a further example, the ionic conductivity may be at least about 1000 μS / cm. Calcination may be performed at a temperature in the range of about 650 ° C to about 1000 ° C.

The resulting cerium oxide fine particles can have desirable properties, particularly for abrasive applications. For example, the cerium oxide fine particles may have a primary particle size in the range of about 70 nm to about 120 nm. As another example, the cerium oxide fine particles may have a secondary particle size in the range of about 80 nm to about 199 nm. In addition, the cerium oxide fine particles may have a density of at least about 6.6 g / cm ³ .

According to one embodiment of the invention, the cerium oxide abrasive material is formed through a precipitation process. For example, the base may be added to a solution comprising cerium salt or the cerium salt may be added to a solution containing base. In particular, the solution may be an aqueous solution of cerium salt. Examples of cerium salts include cerium nitrate, cerium chloride, cerium hydroxide, cerium carbonate, cerium sulfate, or combinations thereof. In certain embodiments, the cerium (III) salt comprises cerium nitrate.

Although various bases can be used, the treatment typically involves mixing a metal hydroxide base with an aqueous solution of cerium (III) salt. The metal hydroxide base can be a base formed from an alkali metal or a base formed from an alkaline earth metal. In particular, examples of metal hydroxide bases include potassium hydroxide (KOH), sodium hydroxide (NaOH), or combinations thereof. In an exemplary embodiment, potassium hydroxide is mixed with an aqueous solution of cerium nitrate.

In one embodiment, the mixture is aged. For example, the mixture may be stirred for at least 8 hours, for example at least 12 hours, at least 16 hours, or even at least 24 hours. Aging can be performed at room temperature. Alternatively, aging may be performed at a temperature of at least 80 ° C.

In addition, the mixture is washed to provide the desired ionic conductivity. Ionic conductivity is typically measured by placing an ionic conductivity probe in a mixture. When an alkali metal base is used to precipitate cerium oxide, the ionic conductivity can indicate the level of alkali metal ions remaining, for example potassium ions. In particular, the washing is performed to retain at least some of the potassium ions. In one embodiment, the mixture may be washed to have an ionic conductivity of at least about 500 μS / cm. For example, the ionic conductivity after washing may be at least about 800 μS / cm, for example at least about 1000 μS / cm, at least about 1100 μS / cm, or even at least about 1400 μS / cm. In particular, the ionic conductivity may be as high as or higher than at least about 1500 μS / cm, or even 2500 μS / cm. In general, the ionic conductivity is about 3500 μS / cm or less, for example 3000 μS / cm or less.

In addition, the mixture may be dried to obtain particulate ceria material in powder form. For example, the mixture can be dried using, for example, a spray drying, freeze drying, or pan drying process. In general, different cohesive properties can be achieved by selecting a drying process. For example, fan drying may be carried out at low temperatures such as approximately room temperature. Alternatively, fan drying may be performed at higher temperatures such as at least about 100 ° C. In general, spray drying is performed at temperatures above 100 ° C., such as at least about 200 ° C. Freeze drying involves freezing the slurry to a solid state, and then heating it under vacuum (about 350 m torr) up to 100 ° C., which process is known to produce less aggregated powders.

The dried cerium oxide fine particles are thermally treated using, for example, a calcination process at a temperature sufficient to promote crystal growth and increase density in the particulate ceria material. Typically, the heat treatment is performed at a temperature of at least about 650 ° C., but up to about 1000 ° C. At temperatures below about 650 ° C., the desired crystal growth will typically not occur in the ceria material, while at temperatures above about 1000 ° C., the ceria particles may exhibit an angular shape, which is an abrasive defect. Leads to. In one embodiment, the calcination temperature may range from about 700 ° C to about 850 ° C. For example, the calcination temperature may range from about 750 ° C to about 825 ° C.

In one embodiment, the calcined ceria material is wet milled to obtain the desired secondary cerium oxide particle size distribution. For example, the calcined ceria material may be wetted and milled with an aqueous solution. The wet milling process can be carried out by adding up to 30% by weight of ceria powder to deionized water with a pH preset. In one example, high purity ZrO ₂ milling media of 0.3-0.4 mm can be used during milling. Slurry milling time is determined by the intended particle size distribution.

In addition, the ceria material may be subjected to an ion exchange process to remove metal ions, such as alkali metal ions. In one example, the ion exchange process may comprise a fluidized-bed ion exchange process. Alternatively, a fixed-bed ion exchange process can be used. The ceria material may also be filtered or concentrated.

In certain embodiments, the ceria material may be combined into a slurry formulation. In one example, the slurry formulation is an aqueous slurry formulation. Alternatively, the slurry formulation may be an organic based slurry formulation. In addition, slurry formulations may include detergents, biocides, and other additives. For example, slurry formulations may include low molecular weight polymer additives, such as polyacrylate based additives. In another example, the slurry formulation can have a preferred pH, eg, a pH above 5, or a pH of at least about 7. The pH can be manipulated, for example, using bases such as ammonium hydroxide, which do not contain alkali metals or alkaline earth metals.

In particular, the process described above provides cerium oxide particles, for example cerium (IV) particles, with desirable properties. Such properties have surprisingly been found to produce polishing slurries which, when used to polish surfaces, for example silica surfaces, yield both desirable surface properties and removal rates. For example, cerium oxide particles have a primary particle size in the range of about 70 nm to about 120 nm. In some embodiments, the cerium oxide particles have a primary particle size in the range of about 70 nm to about 100 nm, such as in the range of about 80 nm to about 100 nm.

As used herein, primary particle size is used to indicate the average longest or length dimension of the particles. For example, when the cerium oxide particles exhibit a spherical or nearly spherical shape, the particle size can be used to represent the average particle diameter. The average particle size can be determined by taking a number of representative samples and measuring the particle size identified in the representative sample images. Such sample images can be taken by various characterization techniques, for example by scanning electron microscopy (SEM). Particle size relates to individually identifiable particles.

In addition, the cerium oxide particles may have a secondary particle size of about 80 nm to about 199 nm. In one embodiment, the secondary particle size may range from about 80 nm to about 175 nm, such as from about 80 nm to about 149 nm. In particular, the secondary particle size may range from about 140 nm to about 149 nm. Secondary particle size can be measured using light scattering techniques such as Horiba LA-920 laser particle size analyzer and Malvern Zetasizer.

In addition to the particle size, the morphology of the ceria material can be further characterized in terms of specific surface area. The specific surface area can be obtained by gas adsorption using the Brunauer Emmett Teller (BET) method. According to embodiments herein, the ceria material comprises cerium oxide particles having a specific surface area in the range of about 5 m ² / g to about 15 m ² / g. In one embodiment, the cerium oxide particles have a specific surface area in the range of about 6 m ² / g to about 13 m ² / g, for example about 6 m ² / g to about 10 m ² / g.

In addition, the cerium oxide particles have a density of at least about 6.6 g / cm ³ . For example, the density may be at least about 7.0 g / cm ³ . In one embodiment, the cerium oxide particles may be a density in the range of about 6.6g / cm ³ to about 7.2g / cm ^3.

In certain embodiments, secondary particle sizes can be determined through calculation, measurement, or a combination thereof. In general, secondary particle size is an indicator of the degree of aggregation or fusion of primary particles. For example, secondary particle size can be calculated based on the BET specific surface area. In another example, secondary particle size can be measured using laser diffraction, for example using a Horiba LA-920 laser particle size analyzer. In special circumstances, the industry characterizes ceria materials in terms of the ratio of the size measured from laser scattering technology to the size calculated from the BET specific surface area. The cerium oxide material may exhibit a ratio of less than 3.0, for example, 2.5 or less. In one example, the ratio is in the range of 1.0 to 3.0, for example 1.2 to 2.2.

In addition, such cerium materials can be characterized by the method outlined by Kwon et al. (US Pat. No. 7,090,821). As determined according to the method outlined by Vol. Et al., The ceria material may have an α cohesion measure of at least about 2.0 and a β cohesion measure of 3.0 or less.

In an exemplary embodiment, the resulting ceria material may comprise polycrystalline cerium oxide particles or a mixture of monocrystalline cerium oxide particles and polycrystalline cerium oxide particles. In one embodiment, the ratio of monocrystalline cerium oxide particles to polycrystalline cerium oxide particles is in the range of 1: 9 to 9: 1. For example, the ratio may be 1: 3 to 3: 1. Alternatively, the ceria material may be predominantly polycrystalline.

In addition, the ceria material is substantially free of lattice substituting impurity, for example titanium. For example, the ceria material may be at least 99.0 wt% cerium oxide such as at least about 99.5 wt% cerium oxide, or even more than 99.9 wt% cerium oxide.

In addition, the ceria material may have the desired particle form. For example, the particles of ceria material may be substantially rounded. "Circular" means particles having an aspect ratio (eg, the first dimension divided by the longest dimension), excluding a cube, of about 1. In particular, the ceria material may have an average roundness of 1.28 or less, for example 1.24 or less, which is defined as the average ratio of dimensions to a set of particles. For example, the average roundness may be 1.2 or less, for example 1.15 or less.

The ceria material described above exhibits desirable properties, in particular with respect to the polishing slurry. In particular, the method described above enables the formation of ceria materials having controlled properties, which provide unexpected technical advantages over prior art ceria materials when used in abrasive slurries.

Typically, the literature focused on low density ceria materials. For example, Yoshida et al. (See, eg, US Pat. No. 6,343,976, US Pat. No. 6,863,700, and US Pat. No. 7,115,021) describe techniques for forming ceria particulate from fired cerium carbonate material. It starts. Such techniques typically lead to low density porous materials, the use of which is supported by Yoshida et al. While other literature information discloses the precipitation of ceria materials (see, for example, US Pat. No. 5,938,837 or US Pat. No. 6,706,082), such literature information is a technique for producing low density materials or for producing small particle size materials. Initiate.

In contrast to the teaching of the literature, Applicants have found that higher density ceria materials of a particular particle size provide improved abrasive slurries. In particular, when such polishing slurry is used to polish silica substrates, the polishing slurry provides a high removal rate and also provides a polished surface with excellent surface finish. Moreover, Applicants provide ceria materials that provide the desired abrasive properties when used in connection with abrasive slurries, the use of special process features including firing ceria material in the presence of certain ions, followed by wet milling and ion exchange. Figured out.

Example

Example 1

An aqueous solution of 31.2% cerium nitrate (III) (20003 g) is titrated with 5000 g of 30% ammonium hydroxide (NH ₄ OH) solution under vigorous stirring. The mixture is washed at room temperature and aged at 90 ° C. for 18 hours. The final ion conductivity is 8500 μS / cm. The mixture is heat treated via autoclaving at a temperature of 220 ° C. The resulting cerium oxide particles are wet milled and filtered at solid loading up to 30% by weight in a pH range of 3.5 to 6 to produce a ceria material. The ceria material comprises cerium oxide particles having a secondary particle size of 90 nm, a specific surface area of 70 m ² / g, and a density of 6.22 g / cm ³ . The particle shape is spherical or nearly spherical and produces an excellent surface finish with a material removal rate (MRR) of 1000 kW / min.

Example 2

An aqueous solution of 31.2% cerium nitrate (III) (20003 g) is titrated with 5000 g of 30% ammonium hydroxide (NH ₄ OH) solution under vigorous stirring. The mixture is aged for 18 hours at room temperature and washed to bring the ionic conductivity to about 570 μS / cm. The mixture is dried and heat treated by calcination in a box furnace at a temperature of 900 ° C. for 2 hours and cooled to room temperature. The resulting cerium oxide particles are wet milled and filtered at solid loading up to 30% by weight in a pH range of 3.5 to 6 to produce a ceria material. The ceria material comprises cerium oxide particles having a secondary particle size of 99 nm, a specific surface area of 31.7 m ² / g, and a density of 6.82 g / cm ³ . The particle shape varies and produces an acceptable surface finish with a material removal rate (MRR) of 4200 kW / min.

Example 3

An aqueous solution of 31.2% cerium nitrate (III) (20003 g) is titrated with 5000 g of 30% ammonium hydroxide (NH ₄ OH) solution under vigorous stirring. The mixture is aged for 18 hours at room temperature and washed to bring the ionic conductivity to 6200 μS / cm. The mixture is dried and heat treated by calcination in a box at a temperature of 900 ° C. for 2 hours and cooled to room temperature. The resulting cerium oxide particles are wet milled and filtered at solid loading up to 30% by weight in a pH range of 3.5 to 6 to produce a ceria material. The ceria material comprises cerium oxide particles having a secondary particle size of 95 nm, a specific surface area of 32.5 m ² / g, and a density of 6.84 g / cm ³ . The particle shape varies and produces an acceptable surface finish with a material removal rate (MRR) of 4200 kW / min.

Example 4

An aqueous solution of 31.2% cerium (III) nitrate (20003g) is titrated with 5000g of 30% ammonium hydroxide (NH ₄ OH) base solution. The mixture is aged for 18 hours at room temperature and washed to give an ionic conductivity of 23,300 μS / cm. The mixture is dried and heat treated by calcination in a box furnace at a temperature of 1100 ° C. for 2 hours and cooled to room temperature. The resulting cerium oxide particles are wet milled and filtered at solid loading up to 30% by weight in a pH range of 3.5 to 6 to produce a ceria material. The ceria material comprises cerium oxide particles having a secondary particle size of 97 nm, a specific surface area of 35.7 m ² / g, and a density of 6.71 g / cm ³ . The particle shape is an angular shape and produces poor surface finish with a material removal rate (MRR) of 4000 kV / min.

Example 5

An aqueous solution of cerium nitrate is precipitated with 22.5% by weight potassium hydroxide (KOH) base. The mixture is aged at room temperature for 18 hours. The mixture is washed to have an ionic conductivity of 49 μS / cm. The mixture is dried and heat treated by calcination in a box furnace at a temperature of 845 ° C. for 2 hours and cooled to room temperature. The ceria material comprises cerium oxide particles having a secondary particle size of 99 nm, a specific surface area of 31.0 m ² / g, and a density of 6.78 g / cm ³ . The particle shape varies and produces an acceptable surface finish with a material removal rate (MRR) of 3700 kPa / min.

Example 6

An aqueous solution of cerium nitrate is precipitated with 22.5% by weight potassium hydroxide (KOH) base. The mixture is aged at room temperature for 18 hours. The mixture is washed to bring the ionic conductivity to 1120 μS / cm. The mixture is dried and heat treated by calcination in a box at a temperature of 800 ° C. for 2 hours and cooled to room temperature. The resulting cerium oxide particles are wet milled and filtered at solid loading up to 30% by weight in a pH range of 3.5 to 6 to produce a ceria material. The ceria material comprises cerium oxide particles having a secondary particle size of 143 nm, a specific surface area of 10.36 m ² / g, and a density of 7.13 g / cm ³ . The particle shape is spherical or nearly spherical and produces an average surface finish with a material removal rate (MRR) of 2500 kW / min.

Example 7

An aqueous solution of cerium nitrate is precipitated with 22.5% by weight potassium hydroxide (KOH) base. The mixture is aged at room temperature for 18 hours. The mixture is washed to bring the ionic conductivity to 1428 μS / cm. The mixture is dried and heat treated by calcination in a box at a temperature of 800 ° C. for 2 hours and cooled to room temperature. The resulting cerium oxide particles are wet milled at solids loading up to 30% by weight in a pH range of 3.5-6. The cerium oxide is then treated via ion exchange in a mixed-bed resin (cation to anion ratio = 1) with a resin to ceria ratio = 2: 1. After 2 hours of ion exchange, the resin is separated and discarded, and the cerium oxide particles are filtered to produce a ceria material. The ceria material comprises cerium oxide particles having a secondary particle size of 197 nm, a specific surface area of 6.85 m ² / g, and a density of 6.76 g / cm ³ . The particle shape is spherical or nearly spherical and produces poor surface finish with a material removal rate (MRR) of 4050 dl / min.

Example 8

An aqueous solution of cerium nitrate is precipitated with 22.5% by weight potassium hydroxide (KOH) base. The mixture is aged for 18 hours at room temperature and washed to bring the ionic conductivity to 1428 μS / cm. The mixture is dried and heat treated by calcination in a box at a temperature of 800 ° C. for 2 hours and cooled to room temperature. The resulting cerium oxide particles are wet milled at solids loading up to 30% by weight in a pH range of 3.5-6. The cerium oxide is then treated via ion exchange in a mixed phase resin (cation to anion ratio = 1) with a resin to ceria ratio = 2: 1. After 2 hours of ion exchange, the resin is separated and discarded, and the cerium oxide particles are filtered to produce a ceria material. The ceria material comprises cerium oxide particles having a secondary particle size of 186 nm, a specific surface area of 7.18 m ² / g, and a density of 6.81 g / cm ³ . The particle shape is spherical or nearly spherical and produces an average surface finish with a material removal rate (MRR) of 4300 kW / min.

Example 9

An aqueous solution of cerium nitrate is precipitated with 22.5% by weight potassium hydroxide (KOH) base. The mixture is aged for 18 hours and washed to bring the ionic conductivity to 1428 μS / cm. The mixture is dried and heat treated by calcination in a box at a temperature of 800 ° C. for 2 hours and cooled to room temperature. The resulting cerium oxide particles are wet milled at solids loading up to 30% by weight in a pH range of 3.5-6. The cerium oxide is then treated via ion exchange in a mixed phase resin (cation to anion ratio = 1) with a resin to ceria ratio = 2: 1. After 2 hours of ion exchange, the resin is separated and discarded, and the cerium oxide particles are filtered to produce a ceria material. The ceria material comprises cerium oxide particles having a secondary particle size of 164 nm, a specific surface area of 6.48 m ² / g, and a density of 6.83 g / cm ³ . The particle shape is spherical or nearly spherical, producing a good surface finish with a material removal rate (MRR) of 4300 kW / min.

Example 10

An aqueous solution of cerium nitrate is precipitated with 22.5% by weight potassium hydroxide (KOH) base. The mixture is aged for 18 hours at room temperature and washed to bring the ionic conductivity to 1428 μS / cm. The mixture is dried and heat treated by calcination in a box at a temperature of 800 ° C. for 2 hours and cooled to room temperature. The resulting cerium oxide particles are wet milled at solids loading up to 30% by weight in a pH range of 3.5-6. The cerium oxide is then treated via ion exchange in a mixed phase resin (cation to anion ratio = 1) with a resin to ceria ratio = 2: 1. After 2 hours of ion exchange, the resin is separated and discarded, and the cerium oxide particles are filtered to produce a ceria material. The ceria material comprises cerium oxide particles having a secondary particle size of 148 nm, a specific surface area of 6.94 m ² / g, and a density of 7.04 g / cm ³ . The particle shape is spherical or nearly spherical and produces excellent surface finish with a material removal rate (MRR) of 4800 kW / min.

Example 11

An aqueous solution of cerium nitrate is precipitated with 22.5% by weight potassium hydroxide (KOH) base. The mixture is aged for 18 hours at room temperature and washed to bring the ionic conductivity to 887 μS / cm. The mixture is dried and heat treated by calcination in a box at a temperature of 800 ° C. for 2 hours and cooled to room temperature. The resulting cerium oxide particles are wet milled at solids loading up to 30% by weight in a pH range of 3.5-6. The cerium oxide is then treated via ion exchange in a mixed phase resin (cation to anion ratio = 1) with a resin to ceria ratio = 2: 1. After 2 hours of ion exchange, the resin is separated and discarded, and the cerium oxide particles are filtered to produce a ceria material. The ceria material comprises cerium oxide particles having a secondary particle size of 146 nm, a specific surface area of 12.11 m ² / g, and a density of 7.14 g / cm ³ . The particle shape is spherical or nearly spherical and produces excellent surface finish with a material removal rate (MRR) of 4700 kW / min.

Example 12

An aqueous solution of cerium nitrate is precipitated with 22.5% by weight potassium hydroxide (KOH) base. The mixture is aged for 18 hours at room temperature and washed to bring the ionic conductivity to 1120 μS / cm. The mixture is dried and heat treated by calcination in a box at a temperature of 800 ° C. for 2 hours and cooled to room temperature. The resulting cerium oxide particles are wet milled at solids loading up to 30% by weight in a pH range of 3.5-6. The cerium oxide is then treated via ion exchange in a mixed phase resin (cation to anion ratio = 1) with a resin to ceria ratio = 2: 1. After 2 hours of ion exchange, the resin is separated and discarded, and the cerium oxide particles are filtered to produce a ceria material. The ceria material comprises cerium oxide particles having a secondary particle size of 143 nm, a specific surface area of 9.29 m ² / g, and a density of 7.11 g / cm ³ . The particle shape is spherical or nearly spherical and produces excellent surface finish with a material removal rate (MRR) of 4700 kW / min.

Table 1 below provides a summary of the process conditions. Table 2 shows the properties of cerium oxide particles such as secondary particle size, specific surface area, density, particle shape, and polishing characteristics resulting from the formation process.

Process conditions Example Titration base Conductivity-Before Heat Treatment
(μS / cm) Heat treatment temperature (℃) Ion exchange
(Yes No) Example 1 NH ₄ OH 8500 220 no Example 2 NH ₄ OH 570 900 no Example 3 NH ₄ OH 6200 900 no Example 4 NH ₄ OH 23300 1100 no Example 5 KOH 49 845 no Example 6 KOH 1120 800 no Example 7 KOH 1428 800 Yes Example 8 KOH 1428 800 Yes Example 9 KOH 1428 800 Yes Example 10 KOH 1428 800 Yes Example 11 KOH 887 800 Yes Example 12 KOH 1120 800 Yes

Particle Characteristics and Polishing Performance Example Secondary
PSD (nm) SSA
(m ² / g) density
(g / cc) Particle shape MRR
(Å / min) Surface finish Example 1 90 70.0 6.22 Roundness 1000 Excellence Example 2 99 31.7 6.82 Various 4200 Great Example 3 95 32.5 6.84 Various 4200 Great Example 4 97 35.7 6.71 Angle 4000 Bad Example 5 99 31.0 6.78 Various 3700 Great Example 6 143 10.36 7.13 Roundness 2500 Average Example 7 197 6.85 6.76 Roundness 4050 Bad Example 8 186 7.18 6.81 Roundness 4300 Average Example 9 164 6.48 6.83 Roundness 4300 Great Example 10 148 6.94 7.04 Roundness 4800 Excellence Example 11 146 12.11 7.14 Roundness 4700 Excellence Example 12 143 9.29 7.11 Roundness 4700 Excellence

Polishing performance is measured by testing the sample slurry in a chemical mechanical planarization (CMP) process. Chemical mechanical planarization (CMP) is performed using an IPEC 372 polishing tool and a K-grooved IC 1400 polishing pad. The wafer carrier speed is set at 40 rpm with a table speed of 45 rpm. The ceria slurry flow rate is 125 mL / min and the ceria solids loading is 1.2%. The test is run on an 8 "PETEOS wafer for 60 seconds. The removal rate is calculated based on the weight loss of the wafer.

As shown in Example 1, precipitation of cerium oxide and heat treatment at temperatures below 600 ° C. provide low density ceria materials with poor material removal rate (MRR). However, as shown in Examples 2, 3, and 4, increasing the heat treatment temperature increases MRR, but decreases the quality of the polished surface.

In Examples 5 to 12, cerium oxide is precipitated using potassium hydroxide. In general, Applicants have surprisingly found that the use of potassium hydroxide allows lower calcination temperatures than using ammonium hydroxide. In addition, Applicants have surprisingly found that potassium hydroxide affects particle growth and polishing performance.

In Example 5, potassium hydroxide is washed to a low ionic conductivity before drying and calcining. The resulting material exhibits reasonable MRR and good surface quality. In Example 6, ionic conductivity is maintained above 1000 μS / cm before drying and calcination, but potassium ions still remain in the final particulate material. The resulting material exhibits a reduced MRR and produces a worse surface finish compared to Example 5.

In contrast, Examples 7-12 maintain ionic conductivity above 500 μS / cm before heat treatment, heat treatment at temperatures above 650 ° C., and perform ion exchange on the resulting powder. Each of Examples 7-12 shows a significantly improved MRR over Examples 5 and 6.

Examples 7-9 show the preferred MRR, but the ceria materials of these examples produce a lower quality surface finish. In contrast, Examples 10-12 show much higher MRRs and provide excellent surface finish. Applicants view the difference in surface finish as a result of smaller secondary particle size distribution and greater density.

Example 13

In particular, Applicants have found that certain combinations of ionic conductivity, calcination temperature, wet milling, and ion exchange treatment can be used to promote crystal growth in ceria materials and provide desirable polishing performance.

For example, FIGS. 1, 2 and 3 show SEM images of particles treated at a calcination temperature of about 775 ° C. and having ion conductivity of 1000 μS / cm, 1500 μS / cm, and 2500 μS / cm, respectively. Generally, particle size increases with increasing ionic conductivity. The particles of FIG. 1 have an average particle size of about 63.0 nm, the particles of FIG. 2 have an average particle size of about 93.5 nm, and the particles of FIG. 3 have an average particle size of about 103.8 nm. This average is determined based on the average diameter of at least five representative particles.

In another embodiment, FIGS. 4, 5, and 6 show SEM images of particles processed at a calcination temperature of about 800 ° C. and with ion conductivity of 1000 μS / cm, 1500 μS / cm, and 2500 μS / cm, respectively. The particles of FIG. 4 have an average particle size of about 102.8 nm, the particles of FIG. 5 have an average particle size of about 110.0 nm, and the particles of FIG. 6 have an average particle size of about 126.0 nm. In yet another embodiment, FIGS. 7, 8, and 9 show SEM images of particles that are processed at a calcination temperature of about 825 ° C. and have ionic conductivity of 1000 μS / cm, 1500 μS / cm, and 2500 μS / cm, respectively. The particle of FIG. 7 has an average particle size of about 113.8 nm, the particle of FIG. 8 has an average particle size of about 114.3 nm, and the particle of FIG. 9 has an average particle size of about 196.8 nm.

As shown in FIGS. 1-9, a combination of ionic conductivity and calcination temperature can be used to manipulate particle growth to produce particles with desirable properties and morphology, particles useful for forming abrasive slurries exhibiting particularly desirable performance. Can be. In particular, for a given ionic conductivity, a 50 ° C. increase in calcination temperature results in an increase of at least 20% in average particle size, for example an increase of at least 50%, or even as high as 80%. Growth index is defined as the percent increase in average particle size resulting from a 50 ° C. change in temperature when the starting temperature is in the range of 750 ° C. to 800 ° C. Thus, the cerium oxide powder producing the particles of FIGS. 1-9 has a growth index of at least about 20, for example at least about 50, or even at least about 80. For a given calcination temperature, a 1500 μS / cm increase in ionic conductivity can result in an increase of at least 20% in average particle size, for example at least 40%, or even as high as 60%. The combined result of a 50 ° C. increase and a 1500 μS / cm increase can provide a 200% increase in particle size.

In addition, the shape of the particles is generally round. For example, the particles of FIG. 7 have an average roundness of 1.17 and a maximum roundness of 1.5. The particles shown in FIG. 9 have an average roundness of 1.12 and a maximum roundness of 1.4. Roundness is the average ratio of one dimension to the next longest dimension.

It is noted that not all of the activities described above in the general description or the examples are necessary, some of which may not be necessary, and that one or more additional activities may be performed in addition to those described. In addition, the order in which the activities are listed does not necessarily have to be the order in which they are performed.

In the foregoing specification, the concepts have been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention.

As used herein, the terms “comprises”, “comprising”, “comprises”, “comprising”, “have”, “having” or any other variation thereof cover a non-exclusive inclusion. I would like to. For example, a process, method, article, or apparatus that includes a list of features is not necessarily limited to those features, and is not specifically listed or incorporates other elements inherent to such process, method, article, or apparatus. It may also include. Moreover, unless expressly stated to the contrary, "or" does not mean " comprehensive " or " exclusive " For example, condition A or B is met by any of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (Or present), both A and B are true (or present).

In addition, the use of the indefinite article “a” or “an” is employed to describe the elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. It is to be understood that such description includes one or at least one, and the singular also includes the plural unless it is obvious that what he otherwise means.

Effects, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, effects, advantages, solutions to problems, and any feature (s) that can generate or become apparent any effect, advantage or solution are very important to any or all of the claims, It should not be interpreted as required or as essential features.

After reading this specification, skilled artisans will appreciate that certain features are described herein in connection with separate embodiments for clarity and may also be provided in combination with a single embodiment. Conversely, various features that are, for brevity, described in connection with a single embodiment, may be provided separately or in any subcombination. Also, reference to values stated within a range includes each and every value within that range.

Claims (64)

A particulate material comprising cerium oxide particles having a secondary particle size distribution ranging from 80 nm to 199 nm and having a density of at least 6.6 g / cm ³ . The particulate material of claim 1, wherein the primary particle size of the cerium oxide particles is in the range of 70 nm to 120 nm. The particulate material of claim 1, wherein the secondary particle size distribution is in the range of 80 nm to 149 nm. The particulate material of claim 3, wherein the secondary particle size distribution ranges from 140 nm to 149 nm. ^{3. The} particulate material of claim 1, wherein the density is at least 7.0 g / cm ³ . The method of claim 1 or claim 2, wherein the particulate material in the range of a density of 6.6g / cm ³ to 7.2g / cm ^3. The particulate material according to claim 1 or 2, wherein the cerium oxide particles have a specific surface area in the range of 5 m ² / g to 15 m ² / g. The particulate material according to claim 7, wherein the cerium oxide particles have a specific surface area of 6 m ² / g to 13 m ² / g. 3. The particulate material of claim 1, wherein the ratio of the calculated secondary particle size of the cerium oxide particles to the secondary particle size distribution of the cerium oxide particles is in the range of 1.0 to 3.0. 4. 10. The particulate material of claim 9, wherein said ratio is in the range of 1.2 to 2.1. The particulate material according to claim 1 or 2, wherein a roundness of the particulate material is 1.28 or less. The particulate material of claim 11, wherein the roundness is 1.24 or less. Mixing an alkaline base with an aqueous solution of cerium nitrate (III);
Aging the mixture to form cerium oxide particles;
Washing the mixture to achieve an ionic conductivity of at least 500 μS / cm; And
And heating the cerium oxide particles at a temperature in the range of 650 ° C to 1000 ° C. The method of claim 13, further comprising wet milling the cerium oxide particles such that the secondary particle size is between 80 nm and 149 nm. The method of claim 14, further comprising removing an alkali metal ion by performing an ion exchange process.








The secondary particle size distribution in the range 90nm to 199nm, and a density of the particulate material is comprising a crystalline cerium oxide particles is 6.6g / cm ³ to 7.2g / cm ^3. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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